Long Term Evolution (LTE) supports higher data rates and spectrum efficiency. LTE uses Single Carrier Frequency Division Multiple Access (SC-FDMA) for transmission in the uplink (UL) direction. LTE implements SC-FDMA as Discrete Fourier Transform Spread Orthogonal Frequency Division Multiplexing (DFT-S-OFDM. A wireless transmit/receive unit (WTRU) in the UL may transmit on a limited, contiguous set of assigned sub-carriers in a Frequency Division Multiple Access (FDMA) arrangement. For purposes of illustration, if the overall Orthogonal Frequency Division Multiplexing (OFDM) signal or system bandwidth in the UL is composed of useful sub-carriers numbered 1 to 100, a first WTRU would be assigned to transmit its own signal on sub-carriers 1-12, a second given WTRU would be assigned to transmit on sub-carriers 13-24, and so on. A base station, such as an evolved NodeB (eNB), may receive the composite UL signal across the entire transmission bandwidth from one or more WTRUs at the same time, but each WTRU may transmit into a subset of the available transmission bandwidth. DFT-S OFDM has the additional constraint that the time-frequency resource assigned to a WTRU may consist of a set of frequency-consecutive sub-carriers.
In LTE UL, WTRUs may transmit their data (and in some cases their control information) on the physical uplink shared channel (PUSCH). The transmission of the PUSCH is scheduled and controlled by the eNodeB using the so-called uplink scheduling grant, which is carried on the physical downlink control channel (PDCCH) format 0. As part of the uplink scheduling grant, the WTRU receives control information on the modulation and coding set (MCS), transmit power control (TPC) command, uplink resources allocation (i.e., the indices of allocated resource blocks), and other similar parameters. The WTRU may then transmit its PUSCH on the allocated uplink resources with the corresponding MCS at the transmit power set by the TPC command.
The transmit power of the WTRU may be determined at the WTRU based on measurements made by the WTRU and the data received from the base station as stated above. WTRU transmit power control may be important for maintaining QoS (Quality of Service), controlling inter-cell interference, and maximizing a terminal's battery life.
LTE-Advanced (LTE-A) supports bandwidth extension using carrier aggregation, UL multiple-input multiple-output (MIMO), simultaneous PUSCH and physical uplink control channel (PUCCH) transmission, and multiple transmit antennas (e.g., up to at least 4 antennas) that may have two codewords (transport blocks) per UL component carrier. Each of these features impacts on WTRU transmit power control.